The present invention relates to magnetic tape drives, and more particularly, to a magnetic tape drive for storage and retrieval of digital data in which an elongate, rectangular tape cartridge is endwise loaded into a rectangular housing.
The five and one-quarter inch Winchester disk drive which provides substantial storage capacity and rapid data access is becoming increasingly popular as a principal memory for personal and small business computers, which until recently, used exclusively flexible or floppy disk memories. A five and one-quarter inch Winchester disk drive may have a memory storage capacity of, for example, fifty-five megabytes. On the other hand, a typical floppy disk drive may have a storage capacity of only one-quarter megabyte.
Many computer systems have backup memory devices to assure against malfunctions or physical damage that could destroy the principal data bank. In the past, in personal and small business computer systems, the backup storage unit has typically consisted of a second floppy disk drive. However, the increasing use of five and one-quarter inch Winchester disk drives in personal and small business computers has created a need for greater backup storage. Floppy disk drives are unsuitable for use as backup storage for a five and one-quarter inch Winchester disk drive because the hard disk stores many times more information than a single floppy disk. For example, forty one-quarter megabyte floppy disks would be needed to backup one ten megabyte Winchester disk drive, making backup storage a time-consuming inconvenience for the operator.
A magnetic tape drive would be a more practical form of backup storage for the five and one-quarter inch Winchester disk drive. Such tape drive would preferably utilize a tape cartridge for convenience and durability. ANSI X3.55-1977 defines a standard one-quarter inch tape cartridge to facilitate industry compatability. One cartridge meeting this standard is the DC300XL cartridge manufactured by Minnesota Mining and Manufacturing. See U.S. Pat. No. 3,692,255. That cartridge measures approximately six inches in length and four inches in width. In addition, the cartridge has a door along one of its longer sides which must be swung open so that the tape drive head can make contact with the tape. This door, when fully open, increases the width of the cartridge from approximately four inches to approximately five and three-quarter inches.
Currently floppy disk drives and five and one-quarter inch Winchester disk drives are constructed to meet an industry standard which requires that they fit within a rectangular box measuring approximately three and one-quarter inches in height by five and three-quarter inches in width by eight inches in length. The foregoing dimensions are hereinafter referred to as the five and one-quarter inch form factor for a mechanical transport. It would be desirable to provide a magnetic tape drive which would fit the foregoing industry mechanical form factor while utilizing the aforementioned 3M cartridge. The magnetic tape transport could then be inserted into the same physical enclosure or hardware designed to receive the five and one-quarter inch Winchester or floppy disk drives.
It is difficult to provide a magnetic tape drive which can receive and utilize the aforementioned 3M tape cartridge in the relatively small industry mechanical form factor. Because the cartridge is six inches in length, it cannot be loaded sideways into such a magnetic tape transport since the width of the mechanical form factor is only five and three-quarter inches. If the tape transport were installed in a receptacle within a mini-computer, there would be no access to the side of the tape drive unless the tape drive could be slid out of the mini-computer. Such sliding out of the entire drive would be undesirable since it would expose sensitive electronic and mechanical components of the drive to possible damage and contamination. Furthermore, such sliding out of the entire drive would require flexible busses and connectors which could fail with repeated use. Accordingly, it would be preferable to load the cartridge endwise into the tape drive. This presents a problem since the width of the cartridge is approximately five and three-quarter inches with the door fully open. Some mechanism would have to provided for opening the door of the cartridge and engaging the head with the tape in an extremely confined amount of space.